Consumers are increasingly interested in milder ways to cleanse their skin which results in less damage of the skin's natural protective barrier and also leads to the retention of more moisture in their skin. Indeed toilet bars based on synthetic surfactant such as the Dove.RTM. Beauty Bar have gained in popularity. Also, milder synthetic based liquids compositions are a growing segment of the market, especially among consumers in the more developed markets around the world.
However, the in-use properties of synthetic based bars and liquids (syndet bars and liquids) are quite different from soap. Synthetic based formulations tend to rinse slowly from the skin, often leave a feeling of a slippery residue remaining on the skin and are perceived not to last as long as soap. For many consumers in warm tropical climates, washing with syndet bars, combo bars and syndet liquids is not perceived to provide the level of cleansing and refreshing in-use sensory experience provided by soap and is a less preferred method of cleansing the skin even though washing with soap is harsher. Furthermore, because of the intrinsic cost of raw materials, packaging (for liquids), and the relatively higher use-up rates, mild syndet and combo bars and liquids makes these products out of reach of most consumers in emerging and developing markets even if they could learn to live with the very different cleansing experience.
There has been a great deal of research and development devoted to making soap bars milder. A recent review is provided by Murahata et al. (Cleansing Bars for Face and Body: In Search of Mildness, in Surfactants in Cosmetics, Ed M. Rieger and L. Rhein, 1997 Marcel Dekker, New York). The approaches include incorporation of relatively high levels of cationic polymers, mild synthetic surfactants, and the inclusion of a relatively high level of glycerol (&gt;10%). All of these approaches have their limitations in terms of cost, manufacturing feasibility and impact on sensory properties and cost. One commercially successful approach is a so called "combo bar" of soap and a synthetic surfactant (e.g., acyl isethionate) as used for example in U.S. Pat. No. 4,954,282 to Resch et al. (relating to Lever 2000.RTM. type product). Even here, the sensory properties, use-up rates and cost do not match those of soap. Thus, there is a very real need for a method of cleansing the skin that is perceived to provide the refreshing cleansing experience and economy of soap while maintaining better skin care especially in the reduction of barrier damage and the increase in the level of moisture retention relative to common soap.
The present invention provides a process for making soap bars which are perceived as effective in removing oil and dirt from skin and are preferred by consumers who like the sensory properties of soap.
The invention further provides a process for making a bar which provides these cleaning and preferred sensory attributes while causing less damage to the skin's naturally protective barrier and while retaining more moisture in the skin than ordinary soap bars.
The invention further provides a method for making a bar which provides these desirable perceived cleaning, and preferred sensory properties, and delivery of improved skin care, yet has a cost that is comparable with soap. In this context "improved skin care" is defined as causing less damage to the skin's naturally protective barrier, retention of more moisture in the skin, and/or reducing visible dryness than the method of cleansing the skin with an ordinary soap bar.
EP Patent No. 0,707,631 to Chambers et al. discloses a soap bar composition comprising:
(a) 44 to 86.5% by wt. fatty acid soap; PA1 (b) 5 to 30% by wt. polyalkylene glycol; PA1 (c) 2.5 to 20% by wt. C.sub.6 to C.sub.22 fatty acid; and PA1 (d) 6 to 20% water. PA1 (a) 50 to 80% by wt. soap; PA1 (b) 4 to 35% by wt. free fatty acid; PA1 (c) 1 to 10% by wt. selected organic salts; and PA1 (d) about 10% water; PA1 (a) 25 to 85% by weight fatty acid soap; PA1 (b) polyalkylene glycol having MW of 400 to 25,000, preferably 400 to 10,000 (an amount such to improve skin condition); and PA1 (c) 1 to 35 C.sub.8 -C.sub.22, preferably C.sub.10 -C.sub.20, more preferably C.sub.10 -C.sub.18 free fatty acid (saturated and unsaturated, preferably at least saturated).
wherein ratio of polyalkylene glycol to C.sub.6 to C.sub.22 fatty acid is 1:3 to 3:1 and polyalkylene glycol has MW below 100,000 Dalton. There is no teaching of the specifically defined protic acid salts of the invention; of the ratios of these salts to free fatty acid; or of the sensory (soap-like clean) and skin care benefits (as measured by defined tests) provided when meeting the defined criteria of the invention.
Applicants have filed a continuation-in-part application to the equivalent of the U.S. Chambers application which claims 0.1 to 50% electrolyte and provides enhanced processing benefits. Again there is no teaching of making a bar using the defined protic acid salts; of ensuring the ratios of these salts to free fatty acid is within defined limits or of enhanced skin care benefits attained in following the process.
Applicants have filed an application to Van Gunst et al. disclosing:
wherein the bar has no more than about 4% synthetic and is processed using standard extrusion equipment.
The reference fails to disclose process for making a bar by adding defined protic acid salts or using ratio of protic acid salts to free fatty acid. The reference fails to disclose enhanced skincare benefits from bars made by such process.
Similarly, U.S. Pat. No. 3,598,746 to Kaniecki discloses soap, free fatty acid and polyalkylene glycol, but fails to recognize sensory properties and skin care benefits as measured in bars made by process of the subject invention.